That has honestly never happened to me.

What has happened was that the phone rebooted in my pocket about 20 times in one day in Legoland. It could not handle the public WiFi provided there that required going through a login portal each time the signal was lost and found again, presumably as I was moving between access points. I do not know what exactly prompted the reboot. Whether it was the browser window timing out or too many browser windows open. I never saw it happening, only that it rebooted again.